Electric furnace.



J. H. GRAY.

ELECTRIC FURNACE.

APPLICATION FILED AUG. 21, 1913.

Patented Oct. 13, 1914.

3 SHEETSSHBET 1.

In INVENTOR Viv W 621.2

J.H.GRAY.

Patented Oct. 13, 1914.

3 SHEETS-SHEET 2.

J.H.GRAY. ELECTRIC FURNACE. APPLICATION FILED AUG.21,1913.

Patented Oct. 13,1914.

3 SHEETS-SHEET 3.

I hm I jwmvmn, M all/5 A TTORNEYS HAM/8%; My

UNITED STATES PATENT OFFICE.

JAMES H. GRAY, OF NEW YORK, N. Y.

ELECTRIC FURNACE.

' Specifieation'of Letters Patent.

Patented Oct. 13, 1914.

4 Application filed August 21, 1913. se'riaim'rsasia.

To all whom it may concern Be it known that 1,1 AMEB H. GnAY, a.citizen of the United States, residing m'the city, county, and-State of New York, have 5 mvented certain new and useful Im rovements in Electric F -nmces,of which t 'e following isa specification.

This invention aims to providea certain improved electric furnace of the Heroult or are type designed for use in melting and refining metals especially in the steel industry; 1

The main objects of the invent-ion are'to provide a furnace of large capacity, well distributed and uniform heat and'economical circuits.

The accompanying drawings illustrate embodiments of the invention.

Figures 1,. 2 and 3 are horizontal sec-- tions of t hree different typesof furnace 'Fig. 4 is a vertical. section of the furnace shown in Fig. 3, showing the electrodes in perspective. Fig;' 5 is a horizontal section of a furnace of larger capacity.

Referring to the embodiments (if the invention illustrated, the furnace is provided with a hearth A for receiving the molten metal B above which are the electrodes C with their lower ends only slightly above the surface so as to form arcs to the metal, the upper ends of the electrodes passing,

through the roof D. The electrodes'arepd:

justable in any usual or suitable way to:

lower them as their lower ends are consumed. The furnace is of a general oblong shape having side walls E and having its ends tapered and rounded as at F in Figs. 1- and 5 or squared as at F, Figs. 2- and with rounded corners.

40 The electrodes are distributed as uniformly as possible over the superficial area of the bath and with uniform distances between the electrodes of each group. Subject ,to these considerations the location of I '46 the electrodes must depend upon the shape of the furnace. The electrodes are also arranged in groups, each group being electrically connected to one transformer or other source of current. Preferably for 60 smaller furnaces, Figs. 1, 2 and 3, there are two groups of three electrodes each, while forlarger furnaces, as in Fig; 5, there are twoend groups of three each and an intermediate group .or groups ha" fourelec- I trodes or any other number 0 electrodes .circuit isarranged in delta, that is with the coils L, M and N arranged in a continuous circuit and each of the conductors O, P and Q connected at a point between two of the coils, so that the current will pass successively down through each one of the electrodes and up through the other two.

In the arrangement shown in Fig. 1 one of the groups of three electrodes 'is at one end of the furnace and the other at the opposite end. In the arrangement of Fig. 3 one of the electrodes of each group is over the middle portion ofthe bath so that to this extent the areas covered by the two groups overlap. In Fig. 2 there is a complete overlapping, each group having one electrode ateach end of the furnace and one at the middle portion thereof. The overlappin of the groups distributes the effects of t e two' oups more uniformly when there is any ifl'erence between the working of the two groups. This is important because of the localization of the heating effect on the metal at and adjacent to the arcs. The com-' I plete overlapping as shown in Fig. 2 has the further advantage of permitting a falrly good operation of the furnace with only one group of electrodes if this should be neces sary or desired for any reason. t

Fig. 5 shows a furnace of approximately the same shape in horizontal section as Fig. 1 and with electrodes in'groups of three at the opposite ends the same as Fig. 1. The

, furnace of Fig. 5, however, is designed for a'larger capacity and is, therefore, made ofextra length, and the space between the end groups of electrodes is covered by an addi= tional'group of four electrodes R, R, R, R equally spaced from each other and from the adjacent electrodes of the end groups. This central group of electrodes is served by a two-phase current which is. transformed through a Scotts connection from a three-phase current; such a connection being indicated diagrammatically at S; T!

and S, T. Thecurrent is alternating, one

phase passing alternately down through R and up through R and in the opposite direction, and the other phase passing similarly through-R and B The tap hole 'U of the furnaces is usually arranged onthe side as shown. In pouring the metal from furnaces of substantially rectangular shape, and especially in smaller furnaces where the banks of the hearth are more nearly vertical there is a tendency of the slag to stick near the corners. This tendency is obviated or materially reduced by making the furnace with taperlling ends as shown in Figs. 1 and 5.

' at I claim is 1. An electric arc furnace for themelting and refining of metals comprisinga hearth for carrying the molten metal, and electrodes above the metal with their lower ends adjacent to the surface thereof to form'an are between each electrode and the metal, said electrodes comprising a plurality of groups of three each, the three electrodes of each group being connected to the respec tive terminals of a three-phase circuit arranged in delta so that the current passes successively down through each electrode and up through the other two electrodes of the group.

2. An electric arc furnace for the melting and refining of metals comprising a hearth for carrying the molten. metal, and electrodes above the metal with their lower ends adjacent to the surface'thereof to form an are between each electrode and the metal, said electrodes comprising a plurality of groups of three each, the three electrodes of each group being connected to the respective terminals of a three-phase circuit arranged in'delta so that the current passes successively down through each electrode and up through the other two electrodes of the group, the area covered by one group overlapping that covered by another group so as to distribute the effect as uniformly as possible.

3. An electric arc furnace for the melting and refining of metals comprising an oblong hearth for carrying the molten metal, and electrodes above the metal with their lower ends adjacent to the surface thereof to form an are between each electrode and the metal, said electrodes being six in number and being arranged in two groups of three each, the three electrodes of each group being connected to the respective terminals of a three-phase circuit arranged in delta so that the current passes successively down through each electrode and up through the other two electrodes of the group.

4. An electric arc furnace for the melting and refining of metals comprising an oblong hearth for carrying "he molten metal,

and electrodes above the metal with their lower ends adjacent to the surface thereof to form an are between each electrode and the metal, said electrodes being six in number and being arranged in twogroups of three each, the three electrodes of each group being connected to the respective terminals of a three-phase circuit arranged in delta so that the current passes successively down through each electrode and up through the other two electrodes of the group, the area of one group overlapping that of the other so as to effect a uniform distribution and so as to permit the operation of the furnace with only one group, if desired.

5. An electric arc furnace for the melting and refining of metals comprising a hearth for carrying molten metal 'and electrodes above the metal Withtheir lower ends adjacent to the surface thereof to form an are between each electrode and the metal, said hearth having-tapered ends and said electrodes comprising groups of three each, one group at each end of the hearth.

6. An electric arc furnace for the meltingand refining of metals comprising a hearth for carrying molten metal and electrodes abovethe metal with their lower ends adjacent to the surface thereof to form an are between each electrode and the metal, said hearth being oblong in shape and said electrodes comprising a plurality of independent groups at opposite ends of the hearth andan additional group of electrodes be tween said endgroups. a 1

7. An electric arc furnace for the melting and refining of metals comprising a hearth for carrying molten metal and electrodes above the metal with their lower ends adjacent to the surface thereof to form an are between each electrodeand the metal, said hearth being oblong in shape and said elec-' trodes comprising two independent groups of three electrodes each at the respective ends of the hearth and an intermediate group of four electrodes spaced equally from each other and from the adjacent electrodes of the end groups.

8. An electric arc furnace for the melting andrefining of metals comprising a hearth for carrying molten metal and electrodes above the metal with their lower ends adjacent to the surface thereof to form an are between each electrode and the metal, said hearth being oblong in shape and said electrodes comprising two independent groups of three electrodes each at the respective ends of the, hearth and an intermediate g"oup of four electrodes, the groups of three electrodes being served with a three phase.

for carrying molten metal and electrodes In Witness whereof, I have hereunto above the metal with their lower ends til signed my name in the presence of two subjaeent .to the surface thereof to form an arc scribing Witnesses. between each electrode and the metal, said JAMES H. GRAY. hearth being of elongated shape in plan and. Witnesses: having its ends tapered and its tap hole at D. ANTHONY UsINA, one ofthe sides. LULU STUBENVOLL.

Copies of this patent may be obtained to: five cents each, by addressing the Commissioner of Patents,

' Wvhinzton, D. 0. 

